The objective of this research is to explain why the anterior chamber of the eye is a so called "privileged site". From our previous work in rats and rabbits showing a mononuclear cell infiltrate within an implant, it is evident that the host does mount an early immune response to skin allografts but that rejection is delayed. The period of survival is relative to the degree of histoincompatibility between the donor and recipient. Since implants placed into the anterior chamber of the eye of orthotopic skin allograft sensitized rats are rapidly rejected, it appears that primary allografts placed into the anterior chamber produce serum factors which prevent the rapid destruction of the graft by the host lymphocytes. The search for either serum blocking or hyporeactive factors will be performed by in vivo experiments utilizing adoptive transfer and graft versus host techniques. In vitro studies will include blocking of both cell mediated reactions and complement mediated serum cytotoxicity reactions. Studies will be performed to explore the possibility of using implants in the anterior chamber of the eye to augment immunosuppression. Principles learned from studies of the anterior chamber of the eye will be applied to other privileged sites of the body.